1. Field of the Invention
The present invention relates to a fuel cell.
2. Description of the Related Art
A direct fuel cell that directly supplies liquid fuel, such as alcohol, to a fuel cell stack does not require an auxiliary machine such as a vaporizer, a reformer, and the like. Therefore, miniaturized batteries used for portable electronic equipment has been expected. In such a known direct fuel cell, such as a circulation-type fuel cell system, an alcohol solution is directly supplied to the fuel cell stack. In operation, protons are extracted, exhaust materials, such as water exhausted from the fuel cell stack, are circulated to a mixing tank which is provided on an upstream side of the fuel cell stack.
A direct methanol fuel cell (DMFC) has the fuel cell stack in which generator cells each including an anode, a cathode and a membrane electrode assembly (MEA) are stacked one on another. In each generator cell, a mixed solution of water and methanol is supplied to the anode via a liquid feed pump or the like, and thus reacts as expressed in the following chemical formula (1). As a result, carbon dioxide is produced. Air is supplied to the cathode via a pneumatic feed pump or the like, and thus reacts as expressed in the following chemical formula (2). As a result, water is produced.CH3OH+H2O→CO2+6H++6e−  (1)3/2O2+6H++6e−→3H2O  (2)
A mixed solution containing water, unreacted methanol and carbon dioxide which has been produced at the anode is discharged from the anode as a gas-liquid two-phase flow. The gas-liquid two-phase flow is separated into a gas and a liquid by a gas-liquid separator provided in an outlet side of a passage of the anode. Separated liquid is circulated to a mixing tank or the like via a collection passage, whereas separated gas is emitted to the atmosphere.
However, the gas-liquid two-phase flow increases the pressure loss in the anode passage when the gas-liquid two-phase flow passes through the anode passage and the outlet side of the passage of the anode. In addition, since the arrangement of the gas-liquid separator increases the anode circulation section in size, it makes it difficult to construct the generator cell in a compact size.